A car bomb hit Syria's second city Aleppo on Sunday, a day after blasts killed 27 in Damascus, and security forces arrested and beat activists at a rare anti-government protest in the capital.

Residents told the British-based Syrian Observatory for Human Rights they saw bodies in the streets of Aleppo, but neither the opposition group nor official media gave numbers of casualties. The Observatory said the blast had been close to a state security office.

State news channel Syria TV said the "terrorist" explosion had been between two residential buildings in the al-Suleimaniya district of Aleppo, behind a post office building.

The opposition reported heavy raids by security forces and fighting with rebels in northern and southern Syrian provinces and suburbs of Damascus.

In the capital, as crowds gathered for memorials to victims of Saturday's car bombs, security forces broke up an opposition march of more than 200 people when protesters began shouting "the people want to topple the regime".

The phrase has echoed through the wave of Arab uprisings that began last year and has toppled autocratic rulers in Tunisia, Egypt, Libya and Yemen.

"They were walking through an area in central Damascus, near SANA (the state news agency). At first they shouted slogans against violence and the police didn't do anything, but as soon as they started to call for regime change the police rushed in and started beating people with canes," said Rami Abdelrahman, from the Syrian Observatory for Human Rights.

An anti-government rally in the capitol is a rarity. The reaction of the police shows why. Assad has buttoned down the two largest cities by using heavy patrols and zero tolerance for defiance.

Eventually, Damascus and Aleppo will join the anti-government uprising as people become emboldened by protests elsewhere. But until then, the protestors will pay the price for speaking out.

Following on the heels of a series of blasts that killed 27 in Damscus yesterday, a car bomb exploded in Syria's second largest city of Aleppo, killing an unknown number.

Also in Damascus, a funeral procession for those killed in Saturday's explosions turned into an impromptu anti-government rally that was quickly crushed by police.

A car bomb hit Syria's second city Aleppo on Sunday, a day after blasts killed 27 in Damascus, and security forces arrested and beat activists at a rare anti-government protest in the capital.

Residents told the British-based Syrian Observatory for Human Rights they saw bodies in the streets of Aleppo, but neither the opposition group nor official media gave numbers of casualties. The Observatory said the blast had been close to a state security office.

State news channel Syria TV said the "terrorist" explosion had been between two residential buildings in the al-Suleimaniya district of Aleppo, behind a post office building.

The opposition reported heavy raids by security forces and fighting with rebels in northern and southern Syrian provinces and suburbs of Damascus.

In the capital, as crowds gathered for memorials to victims of Saturday's car bombs, security forces broke up an opposition march of more than 200 people when protesters began shouting "the people want to topple the regime".

The phrase has echoed through the wave of Arab uprisings that began last year and has toppled autocratic rulers in Tunisia, Egypt, Libya and Yemen.

"They were walking through an area in central Damascus, near SANA (the state news agency). At first they shouted slogans against violence and the police didn't do anything, but as soon as they started to call for regime change the police rushed in and started beating people with canes," said Rami Abdelrahman, from the Syrian Observatory for Human Rights.

An anti-government rally in the capitol is a rarity. The reaction of the police shows why. Assad has buttoned down the two largest cities by using heavy patrols and zero tolerance for defiance.

Eventually, Damascus and Aleppo will join the anti-government uprising as people become emboldened by protests elsewhere. But until then, the protestors will pay the price for speaking out.